Fixing Keyboard and EFI Boot Selection Issues on iMac12,1 after macOS Sequoia Upgrade

Guide Step-by-Step:

If your iMac (Mid 2013) fails to recognise the keyboard at the EFI selection screen after upgrading to macOS Sequoia with OpenCore Legacy Patcher (OCLP), follow these steps to restore functionality. This guide will help you regain access to your EFI selection and boot into macOS.

Step 1: Try a Wired USB Keyboard

1. Connect a Wired Keyboard:
   • Bluetooth keyboards may not connect early in the boot process after an OCLP upgrade. Use a wired USB keyboard for reliable access to the EFI selection screen.
2. Restart the iMac and see if the keyboard allows you to select the EFI partition.

Step 2: Reset SMC (System Management Controller)

1. Unplug the iMac from power and wait 15 seconds.
2. Reconnect the power cable, wait another 5 seconds, then turn on the iMac.
   • An SMC reset can fix USB-related issues and improve peripheral recognition during boot.

Step 3: Reset NVRAM/PRAM

1. With the wired keyboard connected, press Option + Command + P + R immediately after turning on the iMac.
2. Hold these keys for about 20 seconds until the iMac restarts.
   • This resets settings that might interfere with keyboard and USB detection.

Step 4: Boot into macOS Recovery and Reinstall OpenCore Legacy Patcher

1. Access macOS Recovery:
   • Restart and hold Command + R to enter macOS Recovery Mode.
2. Open Terminal in Recovery Mode to mount the EFI:
   • Type the following commands to list disks and mount the EFI:

     bash
     Copy code
     diskutil list
     diskutil mount diskXsY  # Replace X and Y with your external SSD’s EFI partition number
     

3. Download and Install OpenCore Legacy Patcher:
   • If you have another Mac, download OCLP from the OCLP GitHub page.
   • Use OCLP to create a new EFI with updated patches and place it on the EFI partition of your external SSD.

Step 5: Set External SSD as the Default Boot Drive

1. In macOS Recovery, open System Preferences > Startup Disk if accessible.
2. Select your external SSD with macOS Sequoia as the default boot device and restart.

Step 6: Clean Up EFI Entries (Optional)

1. Mount EFI Partitions:
   • Use diskutil list to locate all EFI partitions and mount each using:

     bash
     Copy code
     diskutil mount diskXsY
     

2. Remove Extra EFI Entries:
   • Delete redundant EFI folders or unnecessary OpenCore installations, keeping only the primary EFI folder on the main SSD for a clean boot environment.

Troubleshooting Tips

• Persistent Keyboard Issues: If the wired keyboard doesn’t work, ensure it’s functional by testing it on another computer.
• Multiple EFI Conflicts: Bootloop issues can arise if multiple OpenCore EFIs are present. Remove all but the required EFI folder on the main boot drive.

This guide should help restore keyboard functionality and ensure reliable access to the EFI selection screen on your iMac12,1. Let me know if further assistance is needed!